A prismatic battery having a flat-shaped wound electrode assembly is disclosed in, for example, JP 2013-054998 A. The positive electrode sheet and the negative electrode sheet of the wound electrode assembly disclosed therein have respective mixture layers (also referred to herein as electrode active material layers) formed on respective strip-shaped metal foils. An exposed portion in which the metal foil is exposed is formed along a longer side of the strip-shaped metal foil. The exposed portion of the positive electrode sheet metal foil and the exposed portion of the negative electrode sheet metal foil jut out from the separators in opposite directions at the opposite ends of the winding axis. In these publications, each of the exposed portion of the positive electrode sheet and the exposed portion of the negative electrode sheet metal is divided at the winding center into two sets along the flat thickness direction. Each of the two sets of exposed portions, which are divided along the flat thickness direction, is gathered in the thickness direction.
JP 2013-054998 A discloses the exposed portion of the metal foil in which the starting end of winding is fixed to the inner circumferential surface of the exposed portion that is wound to be an outer peripheral side. JP 2013-045636 also discloses an example of the wound electrode assembly having a construction in which each of the exposed portions of the positive and negative electrode sheet metal foils is divided and gathered into two sets at the winding center along the flat thickness direction.